According to the Manchester evening news, Northern 10p tickets go on sale next week- I think the 14th.
That wouldn't be very helpful when you consider the first date for use is the 13th. Maybe it meant the first dates they could be used?
Northern sent emails out yesterday saying it was to start today, their website also stated it was today and anyone enquiring on Twitter has been told it's still today but just with a delay. The link from the OP now has an update confirming the delay.